The present invention relates to a press-nut adapted to engage with the threads of a bolt, by pressing the nut onto the bolt to receive the bolt in an insertion hole thereof.
A press-nut adapted to engage with the threads of a bolt by pressing the nut onto the bolt to receive the bolt in an insertion hole thereof is disclosed, for example, in Japanese Patent Laid-Open No. 6-81830. The press-nut described in this publication comprises an outer shell body having a nut-like appearance and a tapered inner wall of which the inner diameter is reduced gradually towards an opening at one end thereof; a plurality of split nuts having tapered outer surfaces along the tapered inner wall of the outer shell body and threaded grooves formed on inner walls on the centre side thereof; and a coil spring to push the split nuts up onto the tapered inner wall of the shell body. Since this press-nut engages with the threads of a bolt when it is pressed onto the bolt so as to receive the bolt into an insertion hole, it moves directly to a clamping position when pressed forcefully onto the bolt, eliminating the previously required operation of rotating the nut to the clamping position. A press nut similar to the one described in the above publication is shown in Japanese Patent Laid-Open No. 6-147214, in particular in FIGS. 7 and 8, and in the related description thereof. Such a nut also eliminates any operation to be rotated to the clamping position.
Nevertheless, both of the above press-nuts take time in their assembly, that is, a plurality of split nuts have to be received in a hollow portion of the nut-like outer shell body and the coil spring to press up the split nuts then has to be inserted against the split nuts. These operations require time and labour. Besides, the assembly work requires skill as the coil spring sometimes falls off due to its resilient force. Further, in the nut described in Japanese Patent Laid-Open No. 6-147214, there is a risk of the cover slipping off. Since this press-nut is made of metal as are previously available nuts, split nuts hit each other if vibrated violently to produce noise or to scratch each other. Its manufacture is also time-consuming and costly.